My husband and I will be visiting Reims later this year. We will be traveling by train and don't plan to have a car. We would like to visit some of the champagne houses for tastings, but from what we can tell, many of the champagne houses are 2-3 kilometers from the city center (for example, Pommery, Veuve-Clicquot, and Ruinart). Are there any organized tours in Reims that visit several of the houses, or perhaps visitng both Reims and Epernay, providing the transportation to them? (I know there are day tours from Paris; ideally, we'd like to find something similar in Reims.) If not, is it practical to visit them by taxi?

There are several champagne houses in Reims. They would be easy to visit using taxis or city buses. Here's a web site.
http://www.reims-tourisme.com/indexhtml_br.php

BTW, don't miss the cathedral in Reims. There is a Chagall stained glass window in the back that is absolutely amazing!

Have a good trip.